Mixed coupled azo pigments

ABSTRACT

(1) A mixed coupled azo pigment prepared from: 
     (A) 30% to 70% of two or more diazonium components, at least one derived from a monoaryl amine and 
     (B) an organic coupled component, said pigment containing one or more COOH or . .SO H.!. .Iadd.SO 3  H .Iaddend.groups or esters, amides, alkali metal or alkali earth metal salts thereof or 
     (2) A mixed coupled azo pigment prepared from: 
     (A) 5% to 95% of two or more bis, tris or tetrakis diazonium components, at least one derived from a monoaryl amine and meeting certain specific critria and 
     (B) an organic coupling component, said pigment comprising the same acid or salt groups of pigment (1).

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of abandoned application Ser.No. 07/734,515, filed on Jul. 23, 1991.

FIELD OF THE INVENTION

The present invention relates to mixed coupled azo pigments and to aprocess for preparing such mixed coupled azo pigments.

BACKGROUND OF THE INVENTION

Organic azo pigments are well known in the art and are particularlyuseful as coloring components in various types of printing inks, paintsand plastics. Azo pigments are characterized as containing one or moreazo groups (i.e., --N═N--). Azo pigments are prepared from variousaromatic amines by a two-step process involving diazotization andcoupling. The choice of amine is determined by the color and propertiesof the dye prepared from the amine, the cost of the amine, the ease ofdiazotization, stability of the diazonium salt, etc.

Diazotization involves treating a primary aryl amine with nitrous acidto form a diazonium salt. The diazonium salt is then reacted with acoupled agent to form the azo pigment. Coupling agents used to prepareazo pigments contain an active hydrogen atom bound to a carbon atom, andexamples of types of compounds which have been used as azo couplingagents include compounds containing a phenolic hydroxyl group such asphenols and naphthols, aromatic amines, compounds that containenolyzable ketone groups of an aliphatic character and some heterocycliccompounds such as those containing pyrrole, indole, and similar ringsystems.

Azo pigments may be subdivided chemically according to the number of azogroups present in the pigment such as monoazo, diazo, trisazo,tetrakisazo, etc. Diaryl pigments containing coupled mixedbis-diazotized diamines and acid-substituted aromatic amines aredescribed in U.S. Pat. No. 4,968,352. The pigments are obtained bycoupling a bis-diazotized-substituted benzidine and a diazotized primaryaromatic acid amine as well as mixtures or such amines withacetoacetanilides or with pyrazolinones. Generally, the amount of thearomatic acid amine employed ranges from about 0.25 to about 15% byweight of the final pigment, and preferably, the acid amine is used at alevel of about 0.1 to about 15 mole percent based on the moles of theacetoacetanilide coupler. The pigments may be prepared by diazotizing amixture of the benzidine and the aromatic acid amine and thereaftercoupling the diazotized mixture.

U.S. Pat. No. 4,251,441 describes pigments of mixture ormethoxynitrobenzene-azo-methoxy acetanilides. The mixtures are preparedby diazotizing a mixture of 5-nitro-2-amino-anisol and3-nitro-4-amino-anisol and thereafter coupling the diazotized mixturewith acetoacetic acid-o-anisidide. The anisol mixture may contain from75 to 85% by weight of the 5-nitro derivative and from 15 to 25% of the3-nitro derivative. The mixtures obtained are reported to becharacterized by a high tinctorial strength, a high gloss, goodtransparency and good rheological properties.

U.S. Pat. No. 4,602,960 describes modified diarylide pigments. Thepigments contain (a) a pigment which is composed of a tetrazotizedbenzidine coupled to an acetoacetarylide and/or a 1-phenyl-3-methylpyrazole-5-one, and (b) a water-soluble component obtained from asymmetric or asymmetric coupling product of a tetrazotized4,4'-diamino-2,2'-stilbene disulfonic acid and an acetoacetarylideand/or a 1-phenyl-3-methyl-5-pyrazollone.

U.S. Pat. No. 4,885,033 describes pigments based on acetoacetarylidederivatives. The pigment composition which is suitable for use in modernoffset and letter press inks comprises the mixture of

(A) (a) a pigment which may be derived from a mixed coupling of two ormore coupling agents and tetrazotized (or bis-diazo)3,3'-dichlorobenzidine, (b) a dyestuff derived from specified couplingagents onto tetrazotized benzidine-2,2'-disulfonic acid; and optionally(c) a resin; and

(B) (a) a pigment derived from one or more specified coupling agentsonto one or both of tetrazotized 3,3'-dichlorobenzidine and tetrazotized3,3'-dimethoxybenzidine and (b) an aliphatic amine.

The ratio of components (A) and (B) in the pigment composition rangesfrom 35:65 to 95:5. The dyestuff of (B) (a) may include mixed coupledazo pigments prepared from one or more coupling agents with one or twotetrazotized dichloro or dimethoxybenzidines.

Various types of mixed coupled azo pigments are described in Vol. 4, pp.1510-12 or the Colour Index, Third Edition, Revision 1982, Additions andAmendments No. 62, January 1987, Published by the Society of Dyers andColourists. In particular, two types of "mixed couplings" are described.In the case of yellow pigments, each is described as a product of thereaction between a tetrazotized diamine (D) (i.e., a bis-diazocomponent) and two coupling components (E) and (E'). Such reactions arereported to produce three definite compounds, i.e., E-D-E, E'-D-E' andE-D-E'. Specific examples of such yellow pigments identified in thecolor index are C.I. pigment yellow 114, C.I. pigment yellow 126, C.I.pigment yellow 127 and C.I. pigment yellow 176 at page 1512. Redpigments which are "mixed couplings" are described as formed by reactionof one amine (A) and two coupling components (E) and (E'). Such couplingreactions produce a mixture of two components, i.e., A-E and A-E'proportions defined by the concentrations of (E) and (E') in thereaction mixture. It is reported that these reactions in situ canproduce synergistic effects not obtained by physical admixture ot thetwo components. C.I. pigment red 184 and C.I. pigment red 210 areexamples of such mixed couplings found at page 1511.

Czech Patent 235,634 describes a pigment which is prepared through thecoupling of a mixture of diazotized p-amino acetanilide andp-aminobenzamide with 2-hydroxy-3-naphthoyl-o-anisidide. The Czechpatent describes in Example 1, that the coupling is completed by heatingto 60° C. and adding an aqueous solution containing 6 grams of potassiumcolophony followed by 3 grams of calcium chloride. The colophony orcalcium colophony is included in the pigments apparently to provideimproved properties.

SUMMARY OF THE INVENTION

A mixed coupled azo pigment is described which is prepared from

(A) a mixture comprising from about 5 to about 95% by weight of each oftwo or more diazonium components derived from aromatic amines providedthat:

(A-1) if one of the aromatic amines in the mixture contains acarboxamide group, then the other amine in the mixture is adiaryldiamine; or

(A-2) the mixture comprises about 20 to about 80% of each diazoniumcomponent when one of the aromatic amines contains a carboxylic acid,sulfonic acid, or salt thereof, and the other aromatic amine is adiaryldiamine; or

(A-3) the mixture comprises from about 30 to about 70% of each of thediazonium components when the aromatic amines in the mixture contain anitro group; and

(B) an organic coupling component, provided that when the couplingcomponent is a 2-naphthol characterized by the formula ##STR1## whereinR¹ is hydrogen or --COOH, the mixture (A) may comprise from about 5 toabout 95% by weight of each of two or more diazonium components derivedfrom aromatic amines containing carboxamide groups, and the mixture doesnot have to contain a diaryldiamine.

The mixed coupled azo pigments of the present invention involvingcombinations of at least two amines generally exhibit unique performancecharacteristics which are not exhibited by physical admixtures ofpigments prepared from the individual amines and identical couplingcomponents. The pigments of the invention provide unique performancecharacteristics in inks, plastics, coatings, etc.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The performance characteristics of the mixed coupled azo pigments of thepresent invention prepared from a mixture of two or more aromatic aminesand a coupling component are generally superior to the characteristicsobserved for the azo pigments prepared from the individual aromaticamines with the same coupling agent, and the characteristics of mixturesof said individually prepared azo pigments in terms of cleanliness ofhue, transparency, tinctorial strength, etc. In addition, the crystalstructure of the mixed coupled azo pigments of the present invention, asobserved by X-ray diffraction is different from the crystal structure ofthe individual pigments prepared from one of the aromatic amines in thesame coupling agent and is also different from physical mixtures or suchindividually prepared azo pigments.

In one embodiment, the mixed azo pigments of the invention are preparedfrom

(A) a mixture comprising from about 5 to about 95% by weight of each oftwo or more diazonium components derived from aromatic amines providedthat:

(A-1) if one of the aromatic amines in the mixture contains acarboxamide group, then the other amine in the mixture is adiaryldiamine; or

(A-2) the mixture comprises about 20 to about 80% of each diazoniumcomponent when one of the aromatic amines contains a carboxylic acid,sulfonic acid, or salt thereof, and the other aromatic amine is adiaryldiamine; or

(A-3) the mixture comprises from about 30 to about 70% of each of thediazonium components when the aromatic amines in the mixture contain anitro group; and

(B) an organic coupling component, provided that when the couplingcomponent is a 2-naphthol characterized by the formula ##STR2## whereinR¹ is hydrogen or --COOH, the mixture (A) may comprise from about 5 toabout 95% by weight of each of two or more diazonium components derivedfrom aromatic amines containing carboxamide groups, and the mixture doesnot have to contain a diaryldiamine.

In another embodiment, the mixed azo pigments are water-soluble metalsalts of mixed coupled to pigments prepared by coupling a mixturecomprising from about 5% to about 95% by weight of each of two or morediazonium components derived from aromatic amines and an organiccoupling component wherein at least one of the diazonium components orthe coupling component contains an acidic group and the metal is analkaline earth metal, a transition metal or aluminum, provided that themixture comprises from about 20 to about 80% by weight of each of thetwo diazonium components when one of the diazonium components is derivedfrom a diaryl diamine.

The mixed coupled azo pigments of the present invention are prepared byinitially diazotizing a mixture of two or more aromatic amine compoundsto form a mixture of diazonium salts, and thereafter coupling themixture of diazonium salts with a coupling component to form the desiredmixed coupled azo pigments.

A variety of aromatic amines can be utilized in the formation of the azopigments of the present invention. Almost any primary aromatic amine canbe used. The aromatic amines may be monoamines or polyamines containingup to 4 or more amine groups per molecule. Thus, the diazoniumcomponents derived from such amine may contain one diazonium group(monodiazonium), two diazonium groups (bis-diazonium), three diazoniumgroups (tris-diazonium), etc. The aromatic amines may be monocyclicamines such as aniline and its derivatives, or bicyclic amines such asnaphthyl amine. The aromatic amine may also be a biphenylamine orpolyamine such as aminobiphenyl, benzidine, and 3, 3¹, 4, 4¹-biphenyltetramine.

In one embodiment, the aromatic amine is a primary aromatic aminecharacterized by the formula ##STR3## wherein each R is independentlyhydrogen or a halogen, hydrocarbyl, hydrocarbyloxy or nitro group; n is0, 1 or 2; each Y is independently --COOH, --SO₃ H, or the esters oramides or alkali or alkaline earth metal salts thereof; and m is 0, 1 or2, The term "hydrocarbyl" as used in this specification and claims isintended to include hydrocarbons which may contain substituent groupssuch as ether, ester, nitro or halogen which do not materially affectthe hydrocarbon character of the group.

The aromatic amines characterized by Formula I may contain 0, 1 or 2 Rgroups which are independently hydrogen or a halogen, hydrocarbyl,hydrocarbyloxy or nitro group. The halogen compound could be any of thehalogens although chlorine and bromine are generally used with chlorinebeing the most preferred example of a halogen substituent. Thehydrocarbyl groups may independently be alkyl, cycloalkyl, aryl, aralkylor alkaryl groups. For example, if R is an unsubstituted aryl group, thearomatic amine is a biphenyl amine. When R is an alkyl group, the alkylgroup generally will contain from 1 to 4 carbon atoms. When R is ahydrocarbyloxy group. The hydrocarbyl moiety may be any of thehydrocarbyl groups discussed above although the hydrocarbyloxy groupgenerally is an alkoxy group containing from about 1 to about 4 or morecarbon atoms.

The aromatic amines characterized by Formula I also may contain one ortwo acid groups (Y) which may be --COOH, --SO₃ H, or the esters oramides or alkali or alkaline earth metal salts thereof. In one preferredembodiment, the aromatic amine of Formula I contains an SO₃ H group,

Examples of aromatic amines characterized by Formula I where m equals 0which may be utilized in the present invention include analine,2-aminobiphenyl, 4-aminobiphenyl, 2-methoxy aniline (o-anisidine),3-methoxy aniline (m-anisidine), 4-methoxy aniline (p-anisidine),3-nitro-2-methoxy aniline, 4-methoxy-3-nitro aniline, o-toluidine,m-toluidine, p-toluidine, 2-chloro aniline, 3-chloro aniline, 4-chloroaniline, 3-chloro-4-methoxy aniline (3-chloro-p-anisidine),5-chloro-2-methoxy aniline (5-chloro-o-anisidine), 2-chloro-4-methylaniline, 2-chloro-5-methyl aniline, 2-chloro-6-methyl aniline,3-chloro-2-methyl aniline, 3-chloro-4-methyl aniline, 3-chloro-4-methylaniline, 2-nitro aniline, 3-nitro aniline, and 4-nitro aniline.

Examples of aromatic amines characterized by Formula I wherein Y is asulfonic acid group and m is 1 or 2 include 2-aminobenzene sulfonicacid, 4-aminobenzene sulfonic acid, 2-amino-5-methyl benzene sulfonicacid, 2-amino-5-methoxy benzene sulfonic acid, 3-amino-6-methyl benzenesulfonic acid, 2-amino-4-chloro-5-methyl benzene sulfonic acid,2-amino-4-ethyl-5-chloro benzene sulfonic acid, 2-amino4-methyl-5-chlorobenzene sulfonic acid, etc.

Examples of aromatic amines characterized by Formula I wherein Y is acarboxylic acid group, and m is 1 include 2-amino benzoic acid, 3,-aminobenzoic acid, 4-amino benzoic acid, 2-amino-5-methyl benzoic acid,2-amino-6-methyl benzoic acid, 3-amino-2-methyl benzoic acid,2-amino-3-methoxy benzoic acid, 4-amino-3-methoxy benzoic acid,4-amino-5-chloro-2-methoxy benzoic acid, 2-amino-4-chloro benzoic acid,3-amino-4-chloro benzoic acid, etc.

The benzene sulfonic acid and benzoic acid compounds can be used per seor as their esters, amides or salts such as alkali or alkaline earthmetal salts. Examples of preferred esters include the methyl and ethylesters, and examples of preferred salts include the alkali metal saltssuch as the sodium and potassium salts.

The aromatic amines from which the diazonium components are prepared maybe fused cyclic aromatic amine compounds such as compounds derived fromvarious naphthalenes including 1-naphthyl mine, 2-naphthyl amine,2-amine-1-naphthalene sulfonic acid, 4-amine-1-naphthalene sulfonicacid, etc.

Examples of aromatic amines which are biphenyl amines and polyaminesinclude 2-amine biphenyl, 4-amino biphenyl, 4,-4'-diamino biphenyl,3,3'-dichloro-4,4'-diamino biphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diamino biphenyl and 3, 3¹, 4, 4¹-biphenyltetramine.

In one embodiment, the mixture of aromatic amine may contain from about5 to about 95% by weight of each of two or more of the above-describedaromatic amines. When one of the aromatic amines contains a carboxylicacid or sulfonic acid group, or a salt thereof, and the other aromaticamine is a diaryl amine, the amine mixture comprises about 20% to about80% of each of the aromatic amines. When one or more of the aromaticamines in the mixtures contains a nitro substituent, the mixturecomprises from about 30% to about 70% of each of the aromatic amines.

In another embodiment, the mixture of aromatic amines generally willcontain from about 30 to about 70% of at least two amines. In yetanother embodiment the mixture will contain from 40 to 60% of each oftwo amines and may contain additional amines so long as two amines arepresent in amounts of at least 40% by weight of the mixture.

The mixtures comprising at least two diazonium components used inpreparing the pigments of the present invention may be prepared bydiazotizing a mixture of aromatic amines, or the mixture can be preparedby separately diazotizing individual amines and combining the diazotizedamines. Generally, it is convenient to diazotize a mixture of thearomatic amines and to use this diazotized mixture in the subsequentcoupling reaction. The diazotization of the aromatic amines may becarried out in the manners known to those skilled in the art through theuse of alkali metal nitrites or lower alkyl nitrites together with anadequately strong acid such as a mineral acid. Examples of usefulmineral acids include hydrochloric acid and sulfuric acid. Nitrosylsulfuric acid also can be utilized. The diazotization reaction can beconducted at a temperature in the range of from about -20° to +30° C.,preferably from 0° to 20° C.

Although not required, it may be advantageous in some of thediazotization reactions (and in the subsequent coupling reactions) toinclude a surface-active agent such as a non-ionic, anionic or cationicsurface active agent and optionally appropriate organic solvents suchas, for example, glacial acetic acid, lower alkanols, dioxan, formamide,dimethyl formamide, dimethyl sulfoxide, pyridine or N-methylpyrrolidone.

The coupling component useful in preparing the mixed coupled azopigments of the present invention may be any compound capable ofcoupling the diazonium components contained in the mixtures describedabove.

Among the coupling components which have been described previously arephenols, naphthols, aromatic amines, enolizable carbonyl containingcompounds, and heterocyclic compounds such as pyrroles, indoles, andpyrazolones, etc.

The present invention does not depend upon the use of any particularcoupling component, although the above-identified types of couplingcomponent are generally preferred. Particularly preferred couplingcomponents include phenols, naphthols and enolizable carbonyl-containingcompounds.

Naphthol derivatives are particularly useful coupling components, andthese may be represented by the formula ##STR4## wherein R¹ is hydrogen,--COOH, CONHAr, and Ar is an aromatic group. Preferably R¹ is hydrogenor --COOH. Specific examples of such 2-naphthols include: 2-naphthol,3-hydroxy-2-naphthoic acid, and aryl amides wherein Ar is a phenyl,2-methylphenyl, 4-methylphenyl, 2-methoxyphenyl,4-chloro-2-methylphenyl, 3-nitrophenyl, etc.

The coupling component may also be a compound containing an enolizablecarbonyl-containing compound characterized by the formula

    XCH.sub.2 C(O)Y                                            (III)

wherein X is an electron-withdrawing group and Y is a substituted orunsubstituted amino group. Examples of electron-withdrawing groupsinclude --COR, --COOH, --COOR or --CN wherein R is an alkyl or an arylgroup. The amino group Y is generally an aromatic amino group,preferably, a substituted aromatic amino group, preferably, asubstituted aromatic amino group which may be represented by the formula##STR5## wherein B is, for example, phenyl, 2-chloro-phenyl,2-methoxyphenyl, 2-methyl-4-chlorophenyl, etc.

When the electron-withdrawing group X is CH₃ C(O), and Y is an arylamino group, the coupling compound is generally referred to as anacetoacetyl arylide, and these are particularly useful couplingcomponents in the present invention. The acetoacetyl arylides may berepresented by the formula ##STR6## wherein each R² is independentlyhydrogen, halogen, nitro, an alkyl group containing 1 to about 4 carbonatoms, an alkoxy group containing 1 to about 4 carbon atoms or--NHCOCH₃, and o is 0,1,2 or 3. Specific examples of such couplingcomponents include acetoacetanilides such as acetoacetanilide,acetoacectyl-2-methylanilide, acetoacetyl-2-methoxyanilide,acetoacetyl-4-ethoxyanilide, acetoacetyl-2,4-dimethylanilide,acetoacetyl-2-methyl-4chloroanilide,acetoacetyl-2-methoxy-5-chloroanilide,acetoacetyl-2,4-dimethoxy-5-chloranilide andacetoacetyl-2,5-dimethoxy-4-chloranilide.

The coupling reaction for preparing desired mixed coupled azo pigmentsof the present invention may be effected by adding the couplingcomponent to the mixture of diazonium salts, or the mixture of diazoniumsalts can be added to the coupling component. Coupling is generallyeffected at a temperature of from about -20° to about 50° C., preferablyfrom about 0° to about 40° C. As in a diazotization reaction, couplingmay be carried out in the presence of an appropriate organic solventsuch as all of those identified above for the diazotization reaction.

In one embodiment, the coupling component is dissolved in a basicsolution such as an aqueous alkali metal hydroxide solution. In someinstances, it is desirable to reduce the pH of the solution to about5.0-6.0 using an acid such as acetic acid. Generally the mixture ofdiazonium salts is coupled with an approximately stoichiometric amountof a coupling component. That is, one mole of the diazonium mixture iscoupled with about 1 mole of the coupling component.

In one embodiment of the present invention, the dispersibility of thepigment can be improved by adding an alkali-soluble resin-like productsbefore, during, or after the coupling is completed. Various resin-likematerials can be added for this purpose, and these include for example,rosin resins, polymeric rosins, resin soap, chemically modified rosinresins such as rosin-maleinate resins, alkyd resins, and other synthetichydrocarbon resins with a higher acid number, or combinations of theseresin. The resins may be present in a product with free hydroxyl groupsthat are capable of forming a salt, or may be partially or completely inthe form of salts, for example, with alkaline earth metal ions. It mayalso be advantageous to perform the coupling reaction in the presence ofa finely divided insoluble material, for example, alkaline earth metalsulphates and carbonates, titanium dioxide or clay materials or veryfinely divided organic plastic materials.

When the diazonium salts are prepared from acid amines (i.e., thearomatic amines contain an --SO₃ H or a --COOH group), or from couplingcomponents containing an acid function, the azo pigments may beprecipitated upon completion of the coupling reaction of the addition ofa metal base which forms an insoluble sulfonate or carboxylate salt. Themetal base may be a base of alkaline earth metals, transition metals, oraluminum. The transition metals are those in Groups IVA through VIIIA,IB and IIB of the Periodic Table. Specific examples of useful metalsinclude Ca, Ba, Cd, Mn, Zn, Ni, Fe, Co, Cr and Al. Alkaline each metalbases are preferred. Alkaline earth metal bases such as BaCl₂ and CaCl₂are useful for this purpose.

In some applications, it is desirable, in order to achieve the fulltinctorial strength and the desired favorable crystal structure, to heatthe reaction mixture after coupling. For example, the product of thereaction may be heated to reflux temperature for about 1 to 3 hours orat temperatures below 100° C. under pressure in the presence of theabove-described resin soaps or other soluble resins.

The azo pigments are recovered from the water-based reaction slurryafter completion of the precipitation by filtering to form a presscakewhich is washed free of salts and used either as is to prepare flusheswith oleoresinous vehicles or incorporated directly into aqueousdispersions. Alternatively, the washed presscakes can be dried, groundand used in the form of a coarse or finely divided powder. It is oftendesired to heat the pigment to an elevated temperature to improve theproperties of the pigment. For example, the recovered powder may beheated in air in a temperature of at least about 75° C. at atmosphericpressure or at a lower temperature under reduced pressure.

The following examples illustrate the mixed coupled azo pigments of thepresent invention and their methods of preparation. Unless otherwiseindicated in the following examples and elsewhere in the specificationand claims, all parts and percentages are by weight, temperatures are indegrees centigrade and pressures are at or near atmospheric.

The polyamide ink systems used for evaluating some of the pigments is agenerally standard formulation comprising by weight,

10% dry pigment and

90% of a vehicle consisting of:

40% polyamide resin

30% ethanol

24% isopropyl alcohol

6% n-propyl alcohol

The air-dry enamel systems used for evaluating some of the pigments is agenerally standard formulation comprising by weight,

9.3% dry pigment and

90.7% of a vehicle consisting of:

86.4% Cargill #5114 Resin

13.0% mineral spirits

0.6% mixed metal driers

EXAMPLE 1

A mixture of 6.9 grams of soda ash and 300 ml of water is heated to 80°C. with stirring. To the solution there is added 13 grams of2-amino-4-chloro-5-methyl benzene sulfonic acid and 13 grams of2-amino-4-methyl-5-chloro-benzene sulfonic acid, and the mixture isheated to boiling or until complete solution is obtained. To thesolution there is added slowly and carefully 26 grams of concentratedhydrochloric acid with stirring and cooling to 50° C. Using ice and coldwater, the volume of the slurry is adjusted to 850 ml at 4°-5° C. Asolution of 9.1 grams of sodium nitrite dissolved in 30 ml. of water isadded at a rate slow enough to prevent fuming and to form a diazoniumslurry.

In a separate vessel there is added 22.6 grams of sodium hydroxide (50%)and 22.7 grams of β-oxynaphthoic acid to 400 ml. of warm water. Themixture is stirred to complete the solution. The solution is poured intoa larger container and the volume adjusted to 1500 ml. at 15° C. usingcold water and ice as necessary.

The diazonium slurry is added to the β-oxynaphthoic acid solution over aperiod of 10 minutes followed by an additional 10 minutes of stirring tocomplete the coupling. Ice is added to lower the temperance to about 3°C., and a solution of 38 grams of calcium chloride dissolved in 200 ml.of water is added. The mixture is stirred an additional five minutes anda previously prepared solution of 5.4 grams of wood rosin dissolved in 2grams of 50% sodium hydroxide solution and 150 ml. of water at theboiling point of the mixture is added. This mixture then is stirred forten minutes, and the pH is adjusted to about 9.5 with dilute aceticacid. The mixture then is heated to 80° C. at 1° C./min.; flooded to 65°C. or below; filtered; washed with water and dried at 180° C.

When the mixed coupled pigment of this example is evaluated in apolyamide ink system and the results are compared to corresponding dryblends of component pigments (i.e., pigments prepared by couplingβ-oxynaphthoic acid with the individual aromatic amines), theco-precipitated material of this example is moderately darker, redder,more transparent and displays higher print tone gloss. The mixed coupledazo pigment of this example also is significantly higher in tinctorialstrength.

EXAMPLE 2

A mixture of 0.087 mole of 2-amino-4-methyl-5-chloro benzene sulfonicacid and 0.087 mole 2-amino-4-ethyl-5-chloro benzene sulfonic acid isprepared in 350 ml. of water on a hot plate with smooth agitation. Thereis then added 17.2 grams of 50% sodium hydroxide solution while heatingthe mixture to 70°-75° C. with stirring. Stirring is continued until thesolids are completely dissolved. The solution is cooled by stirring to65° C., and to about 0° to -2° C. by the addition of ice. To this cooledmixture there is added 53 grams of concentrated hydrochloric acid (37%)and the mixture is stirred to obtain a smooth slurry. To the smoothslurry there is then added a solution of 12.4 grams of sodium nitritedissolved in 50 ml. of water. The mixture is stirred for one hour whilemaintaining an excess of nitrite at a temperature of 0°-5° C. by theaddition of sodium nitrite or ice as necessary. Excess nitrous acid isthen eliminated by the addition of 2.2 grams of dry sulfamic acid whilekeeping the slurry cold.

A β-naphthol solution is prepared by dissolving 26.5 grams of β-naphtholin 170 ml. of water and 29.2 grams of 50% sodium hydroxide solution. Tothis solution there is added a mixture of 6 grams of sodium acetatedissolved in 170 ml. of cold water, and the final volume is adjusted to800 ml. at 8°-10° C. using cold water and ice as necessary.

The diazonium slurry is added slowly to the β-naphthol solution dropwise in about 25-30 minutes whereupon the pH of the mixture is adjustedto 8.5-9.0 using hydrochloric acid. The mixture is heated to 78°-80° C.at the rate of about 2° per minute and maintained at this temperaturewhile adjusting the pH to 7.5-8.0. To this mixture there is then added30 grams of barium chloride dihydrate crystals, and the mixture isstirred for up to 30 minutes or until an orange to red color conversionoccurs. The temperature of the mixture is raised at a rate of about 1°C. per minute to a temperature of 94°-96° C. and maintained at thistemperature for 10 to 15 minutes. Ice/water is added as necessary todecrease the slurry temperature to below 70° C. The mixture is filtered,washed chloride-free and dried at 60° C. for 24 hours. A dry yield of75.8 grams is obtained. Compared to a 50:50 mixture of a dry blend ofthe azo pigment prepared from the individual acid amines and β-naphthol,the product of this example in an air-dry enamel system is cleaner,brighter and higher in yellow value and tinctorial strength.

EXAMPLE 3

A mixture of 11.2 grams of 50% sodium hydroxide solution, 13.4 grams of2-amino-5-methyl-benzene sulfonic acid . .(o-anisidine).!. and 13.4grams of 2-amino-4-chloro-5-methyl benzene sulfonic acid is prepared,and 300 ml. of water is added with stirring until clear. Ice is added toa volume of 488 ml. and the temperature is 0°±2° C., Concentratedhydrochloric acid (36.2 grams) is added with stirring over a period of 4to 6 minutes. A solution of 10 grams of sodium nitride and 20 ml. ofwater is added, and the resulting mixture is stirred for 15 minutes at10°-12° C. while testing for excess acid with Congo Red and for nitritewith potassium iodide paper.

A solution of 27.9 grams of β-oxynaphthoic acid and 21 grams of 50%sodium hydroxide solution in 400 ml. of water is prepared at 50°-60° C.with stirring. The clear solution is allowed to cool to 30° C. and iceis added to a total volume of 860 ml. at 8°-10° C.

The diazonium solution is added to the β-oxynaphthoic acid solution overa period of 5-8 minutes while maintaining a pH at about 6.0-6.4. The pHis then adjusted to 11.2-11.4 with sodium hydroxide (50% solution). Iceis then added to cool the mixture to 8°-10° C. whereupon a rosinsolution comprising 7.4 grams of 50% sodium hydroxide solution, 21.8grams of wood rosin and 135 ml. of water is added. The pH of the mixtureis adjusted to 9.7-9.9 with acetic acid (70%) while maintaining thetemperature below about 15° C. The mixture is diluted with ice/water toa volume of 1550 ml. After 30 minutes. 40.8 grams of calcium chloridedissolved in 350 ml. of water are added from a dropping funnel over aperiod of 20 minutes. A pH of about 8.5-8.7 is obtained and the mixturestirred for 2 hours below 15° C. The mixture then is heated at a rate of1° C./min. to a temperature of 65° C. After flooding to 40°-45° C., themixture is filtered, and the residue is dried at 70° C. A dry yield of83.7 grams is obtained. Compared to the corresponding dry blends of thepigments obtained from the individual acid amines and the β-oxynaphthoicacid, the mixed coupled azo pigment obtained in this example in apolyamide ink system is much brighter, cleaner, glossier and moretransparent in print tone and displays a cleaner and stronger tint.

EXAMPLE 4

The procedure of Example 3 is repeated except that the2-amino-4-chloro-5-methyl benzene sulfonic acid is replaced by 13.6grams of 2-amino-4-methyl-5-chloro benzene sulfonic acid. The mixedcoupled azo pigment prepared in this manner in a polyamide ink system,compared to corresponding dry blends of the two pigments prepared bycoupling the individual diazonium compounds with β-oxynaphthoic acid, isbrighter, cleaner, and glossier and more transparent in print tone, anddisplays a cleaner and stronger tint.

EXAMPLE 5

A mixture of 0.5 grams of ethylenediamine tetraacetic acid, 26.8 gramsof m-nitro-o-anisidine, 26.8 grams of m-nitro-p-anisidine and 242 ml. ofcold water is prepared and stirred until a smooth slurry is obtained.Concentrated hydrochloric acid (78.8 grams of 37%) is added, and themixture is cooled with ice to 0°±2° C. This temperature is maintainedthroughout the diazotization reaction. A solution of 22.8 grams ofsodium nitrite dissolved in 46 ml. of water is prepared and added slowlyto the mixture which is then stirred for 35-40 minutes while maintainingan excess of nitrite and "Congo Red" acidity at all times. Excessnitrous acid then is destroyed by the addition of 2.2 grams of drysulfamic acid crystals.

In a separate vessel a mixture of 330 ml. of water, 0.5 grams ofethylenediamine tetraacetic acid, 27.4 grams of a 50% solution of sodiumhydroxide and 27.0 grams of sodium acetate is prepared and heated to 50°C. whereupon 70.5 grams of acetoacet-o-anisidide (AAOA) are added. Themixture is stirred for 25-35 minutes at 48°-52° C. or until completelydissolved. Ice and chilled water are then added to achieve a volume of1054 ml. at 6°-10° C. Just prior to effecting the coupling reaction, thepH of the coupling solution is adjusted to 5.4-5.8 using about 34.9grams of 70% acetic acid.

The diazonium solution is added to the AAOA slurry over a period of1.5-2 hours while maintaining a temperature of 12°-15° C. The mixture istested for excess diazonium salt periodically, and this test alwaysshould be negative. If a positive test for diazonium salt is obtained,no additional diazonium salt solution is added until the reactionbalance has been achieved. When the addition of the diazonium iscompleted, the pH should be 3.7-4.2, and is adjusted as necessary. Themixture is stirred for 10-15 minutes and heated to 15° C. at a rate of1° C./min. At the 50° C. temperature, the pH is adjusted to 10.3-10.5 bythe slow addition of 50 grams of a 50% sodium hydroxide solution. When astable pH is obtained a solution comprising 171 ml. of water, 1.6 gramsof sodium hydroxide solution, 3.1 grams of Staybelite resin and 3.1grams of Polypale resin is added over a 20-30 minute period. Afterstirring for an additional 15-20 minutes, a solution of 6.9 grams ofcalcium chloride and 30 ml. of water is added. The pH of the mixture isadjusted to 6.8 to 7.0 with concentrated hydrochloric acid, and thismixture is heated at 1° C./min. to 94°-96° C. This elevated temperatureis maintained for 2.5 hours, and the mixture is then cooled to below 75°C. The cooled mixture is filtered, washed free of chlorine and dried at115° C. for 48 hours. A dry yield of 123 grams is obtained, and themixed coupled pigment obtained when evaluated in an air-dry enamel issignificantly cleaner, brighter and higher in tinctorial strength thandry blends of the individual pigments prepared by coupling theindividual anisidines with AAOA.

EXAMPLE 6

A mixture of 23.9 grams of dichlorobenzidine, (DCB) 29 grams ofconcentrated hydrochloric acid and 245 ml. of ice and water is preparedand stirred for 30 minutes to a smooth slurry. To the slurry there isadded a solution of 13.7 grams of sodium nitrite in 30 ml. of water.Stirring is continued for one hour while maintaining a temperature plusor minus 2° C. and maintaining a strong excess of nitrite in themixture. Sulfamic acid (2.2 grams) is then added as needed to neutralizethe excess nitrite prior to coupling, and the final volume is raised to360 ml. by the addition of water.

A second diazonium salt is prepared from a mixture of 24.4 grams of3,3'dimethoxy benzidine (ortho-dianisidine, ODA), 32.3 grams ofconcentrated hydrochloric acid and 400 ml. of water by stirring themixture to 0° C. for 45 minutes until a smooth slurry is obtained. Theslurry volume is increased to 532 ml. at 4°-6° C., and a solution of15.7 grams of sodium nitrite dissolved in 35 ml. of water is added overperiod of 6 minutes. The temperature of the mixture should be maintainedbelow about 20° C. with the addition of ice if necessary. The mixture isstirred for an additional hour while maintaining an excess of nitriteand hydrochloric acid at all times. Dry sulfamic cold (1.9 grams) isadded to eliminate any excess nitrite before coupling. The final volumeis increased to 570 ml.

A coupling solution is prepared of 36.0 grams of acetoacetanilide (AAA),18.1 grams of a 50% aqueous sodium hydroxide solution and 29.1 grams ofsodium acetate in 400 ml. of water at 40° C. The mixture is stirreduntil dissolved and thereafter cooled to 20°-30° C. About 30 minutesprior to coupling, the volume is adjusted to 900 ml. at 22° C. and about22.5 grams of acetic acid (70%) are added to adjust the pH to 5.0-5.5.

A mixture of 180 ml. of the DCB tetrazonium salt and 285 ml. of the ODAtetrazonium salt is prepared and added dropwise to the coupling solutionover a period of 2 hours while maintaining an excess of theacetoacetanilide at all times. The final pH should be 4.4-4.8. Themixture is stirred an additional ten minutes and then heated to 90° C.at a rate of 1° C./min. The mixture is maintained at this temperaturefor 30 minutes whereupon cold water is added to cool the mixture tobelow 70° C. The mixture is filtered, washed chloride-free and dried at60° C. for 16 hours yielding 29 grams of dry pigment. When evaluated ina polyamide ink system, the mixed coupled azo pigment, compared to a dryblend of the pigments prepared from the DCB or ODA with AAA, is muchlighter, cleaner, yellower and more transparent in mass tone, andyellower, cleaner and stronger in tint application.

The mixed coupled azo pigments of the present invention, as illustratedin the above examples exhibit a high tinctorial strength, a high gloss,good transparency and good rheological properties. In addition to theabove-desirable properties, the mixed coupled azo pigments of thepresent invention also are characterized as having x-ray diffractionpatterns which are distinct from the coupled azo pigments prepared fromthe individual aromatic amines and the coupling component. The x-raydiffraction pattern of the mixed coupled azo pigments of the presentinvention also is different from the x-ray diffraction pattern of aphysical mixture of the individual pigments. To illustrate, a mixedcoupled azo pigment of the present invention prepared from a mixture oftwo amines (A and A') and a coupling component (C) exhibits an x-raydiffraction pattern which is different from the x-ray pattern of thepigment A-C or the pigment A'-C, or a physical mixture of pigments A-Cand A'-C.

Although not wishing to bound by any theory or explanation, it isbelieved that the mixed coupled azo pigment forms a unique crystalstructure wherein one of the coupled pigments acts as a host lattice forthe other pigment. This results in a unique lattice structure and in theproduction of azo pigments having unique and desirable characteristics.

While the invention has been explained in relation to its preferredembodiments, it is to be understood that various modifications thereofwill become apparent to those skilled in the art upon reading thisspecification. Therefore, it is to be understood that the inventiondisclosed herein is intended to cover such modifications as are embracedwithin the scope of the amended claims.

It is claimed:
 1. A mixed coupled azo pigment prepared from(A) a mixturecomprising from about 30% to about 70% by weight of each of twobis-diazonium components derived from aromatic amines provided that atleast one diazonium component is derived from a monoaryl amine; and (B)an organic coupling component provided that at least one of thediazonium components or the coupling component contains one or more--COOH or --SO₃ H group or the esters or amides or alkali metal oralkaline earth metal salts thereof.
 2. The azo pigment of claim 1wherein the coupling component is selected from the group consisting ofphenols, naphthols, aromatic amines, enolizable carbonyl-containingcompounds and heterocyclic compounds selected from the group consistingof pyrroles, indoles and pyrazolones.
 3. The azo pigment of claim 1wherein the coupling component is an arylamide of acetoecetic acid.
 4. Amixed coupled azo pigment prepared from(A) a mixture comprising fromabout 30% to about 70% by weight of each of two or more diazoniumcomponents derived from aromatic amines provided that at least onediazonium component is derived from a monoaryl amine; and (B) an organiccoupling component which is an enolizable carbonyl-containing compoundcharacterized by the formula

    XCH.sub.2 C(O)Y                                            (III)

wherein X is an electron-withdrawing group, and Y is a substituted orunsubstituted amino group provided that at least one of the diazoniumcomponents or the coupling component contains one or more --COOH or--SO₃ H group or the esters or amides or alkali metal or alkaline earthmetal salts thereof.
 5. The azo pigment of claim 4 wherein X is --COR,--COOH, --COOR or --CN wherein R is an alkyl or aryl group.
 6. A mixedcoupled azo pigment prepared from(A) a mixture comprising from about 30%to about 70% by weight of each of two or more diazonium componentsderived from aromatic amines wherein at least one of the diazoniumcomponents in the mixture is derived from an aromatic aminecharacterized by the formula ##STR7## wherein each R is independentlyhydrogen or a halogen, hydrocarbyl, hydrocarbyloxy or nitro group; n is0, 1 or 2; each Y is independently --COOH, --SO₃ H, or the esters oralkali metal salts thereof; and m is 1 or 2; and (B) an organic couplingcomponent which is an enolizable carbonyl-containing compound.
 7. Theazo pigment of claim 6 wherein the mixture (A) comprises from about 40%to about 60% each of the two diazonium components.
 8. The azo pigment ofclaim 6 wherein the coupling component (B) is an enolizablecarbonyl-containing compound characterized by the formula

    XCH.sub.2 C(O)Y                                            (III)

wherein X is an electron-withdrawing group and Y is a substituted orunsubstituted amino group.
 9. The azo pigment of claim 8 wherein theelectron-withdrawing group is --COR, --COOH, --COOH, --COOR or --CNwherein R is an alkyl or an aryl group.
 10. The azo pigment of claim 6wherein n is 2, one R is a halogen, and the other R is an alkyl group.11. The azo pigment of claim 6 wherein Y is --SO₃ H and m is
 1. 12. Theazo pigment of claim 6 wherein the mixture (A) contains two of thediazonium components in approximately equal amounts by weight.
 13. Theazo pigment of claim 6 wherein the coupling component is an arylamide ofacetoacetic acid characterized by the formula ##STR8## wherein each R²is independently hydrogen halogen, nitro, alkyl group containing 1 toabout 4 carbon atoms, alkoxy group containing 1 to about 4 carbon atoms,or --NHCOCH₃ and o is 0, 1, 2 or
 3. 14. A metal salt of a mixed coupledazo pigment prepared by coupling a mixture comprising from about 30% toabout 70% by weight of each of two or more diazonium components derivedfrom aromatic amines with an organic coupling component which is anenolizable carbonyl-containing compound and wherein at least one of thediazonium components is derived from a monoarylamine and contains anacidic group, and the metal is an alkaline earth metal, a transitionmetal or aluminum, or combination thereof.
 15. The metal salt of claim14 wherein the acidic group is a carboxylic acid group or a sulfonicacid group.
 16. The metal salt of claim 14 wherein at least one of thediazonium components is derived from an aromatic amine characterized bythe formula ##STR9## wherein R is independently hydrogen or a halogen,hydrocarbyl, hydrocarbyloxy or nitro group; n is 0, 1 or 2; each Y isindependently --COOH or --SO₃ H; and m is 1 or
 2. 17. The metal salt ofclaim 14 wherein the metal is an alkaline earth metal.
 18. The metalsalt of claim 17 wherein the acidic group is a carboxylic or sulfonicacid group.
 19. The metal salt of claim 17 wherein the acidic group is asulfonic acid group.
 20. The metal salt of claim 17 wherein the metal iscalcium.
 21. The metal salt of claim 17 wherein at least one of thediazonium components is derived from an aromatic amine characterized bythe formula ##STR10## wherein R is independently hydrogen or a halogen,hydrocarbyl, hydrocarbyloxy or nitro group; n is 0, 1 or 2; each Y isindependently --COOH or --SO₃ H; and m is 1 or
 2. 22. The metal salt ofclaim 21 wherein m is
 1. 23. The metal salt of claim 21 wherein Y is--SO₃ H and m is
 1. 24. The metal salt of claim 14 wherein the couplingcomponent is an enolizable carbonyl-containing compound characterized bythe formula

    XCH.sub.2 C(O)Y                                            (III)

wherein X is an electron-withdrawing group and Y is a substituted orunsubstituted amino group.
 25. The metal salt of claim 24 wherein X is--COR, --COOH, --COOR, or --CN wherein R is an alkyl or aryl group. 26.The metal salt of claim 21 wherein the mixture comprises from about 40to about 60% of two diazonium components.
 27. A mixed coupled azopigment prepared from(A) a minute comprising from about 5 to about 95%by weight of each of two or more diazonium components derived fromaromatic amines wherein at least one of the diazonium components is abis-, tris- or tetrakis-diazonium component provided that at least onediazonium component is derived from a monoaryl amine, and furtherprovided: (A-1) if one of the aromatic amines in the mixture contains acarboxamide group, then the other amine in the mixture is adiaryldiamine; or (A-2) the mixture comprises about 20 to about 80% ofeach diazonium component when one of the aromatic amines contains acarboxylic acid, sulfonic acid, or salt thereof, and the other aromaticamine is a diaryldiamine; or (A-3) the mixture comprises from about 30to about 70% of each of the diazonium components when the aromaticamines in the mixture contain a nitro group; and (B) an organic couplingcomponent, provided that at least one of the diazonium component in (A)or the coupling component contains one or more --COOH or --SO₃ H groupor the esters or amides or alkali metal or alkaline or metal saltsthereof, and further provided that when the coupling component is a2-naphthol characterized by the formula ##STR11## wherein R¹ is hydrogenor --COOH, the mixture (A) may comprise from about 5 to about 95% byweight of each of two diazonium components derived from aromatic aminecontaining carboxamide groups, and the mixture does not have to containa diaryldiamine. .Iadd.
 28. A mixed coupled azo pigment prepared from(A)a mixture comprising from about 40% to about 60% by weight of each oftwo diazonium components derived from aromatic amines which are free ofhydrocarbyloxy groups and wherein at least one of the diazoniumcomponents in the mixture is derived from an aromatic aminecharacterized by the formula ##STR12## wherein each R is independentlyhydrogen or a halogen, hydrocarbyl, or nitro group; n is 0, 1 or 2; eachY is independently --COOH, --SO₃ H, or the esters, alkali metal salts oralkaline earth metal salts thereof; and m is 1 or 2; and (B) an organiccoupling component which is a 2-naphthol characterized by the formula##STR13## wherein R¹ is hydrogen or --COOH, or the esters, alkali metalsalts or alkaline earth metal salts thereof. .Iaddend..Iadd.
 29. The azopigment of claim 28 wherein n is 2, one R is a halogen, and the other Ris an alkyl group. .Iaddend..Iadd.30. The azo pigment of claim 28wherein Y is --SO₃ H and m is
 1. .Iaddend..Iadd.31. The azo pigment ofclaim 28 wherein Y is --SO₃ H, m is 1, n is 2 and one R is a halogen andthe other R is an alkyl group. .Iaddend..Iadd.32. The azo pigment ofclaim 28 wherein R¹ is --COOH, an alkali metal or alkaline earth metalsalt thereof, or mixtures of said metal salts. .Iaddend.